Deploy a Sinatra App to Heroku

Deploy a Sinatra app with an encrypted .env.vault file to Heroku.

Initial setup

Install sinatra and rackup to your Gemfile.

bundle add sinatra rackup

Your Gemfile should look something like this.


source ""

gem "sinatra", "~> 3.0"
gem "rackup", "~> 1.0"

Create an index.rb file with the web server code.


require "sinatra"

get "/" do
  "Hello #{ENV["HELLO"]}."

Create your file.

require "./index"
run Sinatra::Application

Add a Procfile to run your app on Heroku.


web: APP_ENV=production bundle exec rackup -p "$PORT"

Commit that to code and push it to Heroku.

heroku create
git push heroku

Once deployed, your app will say 'Hello .' as it doesn't have a way to access the environment variable yet. Let's do that next.

Install dotenv-vault

Install dotenv-vault.

bundle add dotenv-vault

Create a .env file in the root of your project.


# .env

As early as possible in your application, require and load dotenv-vault.


require "dotenv-vault/load"
require "sinatra"

get "/" do
  "Hello #{ENV["HELLO"]}."

Try running it locally.

ruby index.rb
== Sinatra (v3.0.6) has taken the stage on 4567 for development with backup from Puma
* Listening on

It should say Hello World.

Great! ENV now has the keys and values you defined in your .env file. That covers local development. Let's solve for production next.

Build .env.vault

Push your latest .env file changes and edit your production secrets. Learn more about syncing

npx dotenv-vault@latest push
npx dotenv-vault@latest open production

Use the UI to configure those secrets per environment.

Then build your encrypted .env.vault file.

npx dotenv-vault@latest build

Its contents should look something like this.


#/         cloud-agnostic vaulting standard         /
#/   [how it works](   /

# development

# production


Fetch your production DOTENV_KEY.

npx dotenv-vault@latest keys production
# outputs: dotenv://:[email protected]/vault/.env.vault?environment=production

Set DOTENV_KEY on Heroku using the CLI.

heroku config:set DOTENV_KEY='dotenv://:key_1234…'

Or use Heroku's UI.


Commit those changes safely to code and deploy.

That's it! On deploy, your .env.vault file will be decrypted and its production secrets injected as environment variables‚ just in time.

If a DOTENV_KEY is not set (for example when developing on your local machine) it will fall back to standard dotenv functionality.